Helical Pile Coupler Connections

[humanengr]

I'm considering helical piles with relatively large diameter shafts (approximately 12" dia.).
I'm wondering if anyone has experience with this condition. In particular I'm looking for information on what type of bolts or connectors are appropriate to be used for the coupling bolts. To bolt through the coupler and shaft, the length would exceed what is typically available or used for high-strength bolts. I could use threaded rods with nuts on each end. Lock nuts could be used to prevent loosening.
Just wondering if anyone can comment based on tried and tested methods / materials for this situation.
Thank you,

 

[XR250]

I didn't know they made them that big!

 

[dcarr82775]

I have only seen them field welded when they get that large.

 

[WiSEiwish]

I've used them before and the coupler hardware is provided with the pier by the manufacturer. I have not used a 12" diameter shaft though. That seems rather large. What kind of loading do you have? For a 3.5" diameter shaft the capacity of the shaft can be greater than 100 kips allowable.

 

[humanengr]

Its a lateral loading issue. Otherwise much smaller shaft could be used for the helical extension to develop compressive / uplift loads. Conditions don't allow driven piles. ACIP are kind of the default solution but certainly not optimal. Helical piles would save a tremendous duration of time.
Thanks for the input.

 

[jittles]

For lateral loading, could you not use a battered pile?

I'm not sure how that compares cost-wise.

 

[Archie264]

I was surprised that some of you thought 12" is large...until I realized you were talking about the shaft!

 

[dcarr82775]

I assume you will be battering the pile to resist lateral loads

 

[humanengr]

Battered Piles were considered, but generally not an option due to site limitations. In some locations, new piles are being added between two existing foundations that already have battered piles themselves. We're lucky to find space to put in vertical piles, much less try to batter them. Thanks for the feedback and responses.